Dengue virus is endemic throughout tropical regions of the world and threatens over half of the world's population. A vaccine that can protect against infection by all four of the dengue viruses (serotypes DEN-1 through DEN-4) is a critical global health need. The attenuated DEN-2 virus has been shown to be safe, potent and effective, generating long-lasting neutralizing antibody responses in human clinical trials. The mutations that weaken the virus have been characterized and lie outside the DEN-2 structural genes. The attenuated virus has been used as a backbone to express the structural genes of DEN-1, DEN-3 and DEN-4. Each "chimeric" virus bears the distinctive attenuation markers of the original DEN-2 parent and is safe and effective in animal models. Mixing the parent attenuated DEN-2 virus with the three chimeric viruses generates a tetravalent vaccine that can induce immune responses against all four dengue serotypes. We propose to complete the preclinical development of this unique vaccine. We will generate and characterize viral seed stocks required for manufacture of the vaccine. We will undertake formulation studies to optimize the activity of the vaccine. We will test the final, formulated vaccine in critical dengue models. We will develop both industry standard and unique assays to assure the safety, identity and potency of our vaccine. Finally, we will manufacture sufficient quantities of the vaccine to initiate human clinical trials. To achieve these goals, we have formed an international consortium of vaccine and dengue specialists from biotechnology, academia, and government institutions. To facilitate delivery of this vaccine to those that need it most, our unique collaboration includes an Indian manufacturer that globally supplies WHO-approved vaccines. Development of an affordable, safe and effective dengue vaccine will protect those that live in or travel to Asia, Central and South America, the Caribbean, the Pacific Islands, and parts of Africa and Australia.